How JustAnswer Works:

Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.

Get a Professional Answer

Via email, text message, or notification as you wait on our site.Ask follow up questions if you need to.

100% Satisfaction Guarantee

Rate the answer you receive.

Ask Dave Nova Your Own Question

Dave Nova, Chevrolet Technician

Category: Chevy

Satisfied Customers: 18997

Experience: ASE Master Certification. GM World Class Certification

11042942

Type Your Chevy Question Here...

Dave Nova is online now

1994 Caprice Classic: a check engine light..run rough..stalls

Customer Question

I have a 1994 Caprice Classic (5.7). After running fro between 25 to 45 minutes the car get a check engine light and begins to run rough and finally stalls. I have changed the Distributor, Cap and Rotor, MAP Sensor, Ignition Module, and Coil, The plugs and wires are also new. When I allow the car to cool down it runs fine again. Any ideas?

The Engine will restart but the Check Engine Light is still on and it runs rough. If I allow the car to cool completely again it runs fine. If I keep the engine RPM elevated I can drive the car to get where I need to go but once I stop it will stall.

OK I finally got a chance to check the Fuel Pressure. Key on Not srtated it reads 43 psi. Engine warmed up and Check Engine Light on it drops to 37 PSI and remains steady. From what I have read in the ALL DATA manual that is normal.

Hopefully the engine runs better. The problem could be due to an egr valve that is opening prematurely or is sticking open. If this is the case then disconnecting the egr valve would cause the engine to run properly. Try it and let me know what you find.

Currently the Check Engine Light is not on. I am waiting for it to come on and start running rough again. I did unplug the vacuum line anyway and thereseemed to be a very slight increase in engine RPM.

OK here is what happened. THe service Engine light came on and engine waqs starting to run a bit rough. I disconnected the Vacuum Line at the EGR Valve. NO notable difference. However I did notice that if I tried to advance the Throttle quickly the Engine woudl stumble badly and try to stall. If I did a slow steady increase in the Throttle then the Engine only stumbled slightly and was able to keep running.

Customer:replied 3 years ago.

OK here is what happened. THe service Engine light came on and engine waqs starting to run a bit rough. I disconnected the Vacuum Line at the EGR Valve. NO notable difference. However I did notice that if I tried to advance the Throttle quickly the Engine woudl stumble badly and try to stall. If I did a slow steady increase in the Throttle then the Engine only stumbled slightly and was able to keep running.

Customer:replied 3 years ago.

OK here is what happened. THe service Engine light came on and engine waqs starting to run a bit rough. I disconnected the Vacuum Line at the EGR Valve. NO notable difference. However I did notice that if I tried to advance the Throttle quickly the Engine woudl stumble badly and try to stall. If I did a slow steady increase in the Throttle then the Engine only stumbled slightly and was able to keep running. I accidently clicked on the wrong button. Please continue to assist me

Customer:replied 3 years ago.

Hi Dave,

I am not sure if your still getting these messages. I accidently clicked on the wrong button. I am still in need of your assistance. Please continue to assist me

That is your problem. Fuel pressure should actually increase when the throttle is opened. Your fuel pump is not supplying enough fuel to keep up with the demand of the engine. You will need to replace the fuel pump.

Yes, When you tested fuel pressure earlier it looks like the fuel pressure regulator is working to regulate the fuel pressure. The regulator will typically not fail and cause a loss of fuel pressure. 99% of the time it is the fuel pump. You can locate the rubber section of the fuel lines and crimp shut the return line (smaller diameter line) and repeat the test. If the fuel pressure increases greatly with the line crimped off then replace the regulator. If the pressure and the symptoms stay the same, replace the fuel pump.

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. RobinElkton, Maryland

Ask a Chevy Mechanic

Get a Professional Answer. 100% Satisfaction Guaranteed.

69 Chevy Mechanics are Online Now

Type Your Chevy Question Here...

characters left:

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.